<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .demo {
            background-color: orange;
        }
    </style>
</head>

<body>
    <button id="btn">点我创建一个输入框</button>
    <script type="text/javascript">
        const btn = document.getElementById('btn');
        btn.onclick = () => {
            const input = document.createElement('input');
            // input.focus();  //获取焦点操作不奏效
            // input.parentElement.style.backgroundColor= 'skyblue';  //报错
            input.className = 'demo';
            input.value = 99;
            input.onclick = () => { alert(1); };
            document.body.appendChild(input);
            input.focus();
            input.parentElement.style.backgroundColor= 'skyblue';
        };
    </script>
</body>


</html>